1. Field of the Invention
The present invention relates to a reflow soldering apparatus and a reflow soldering method.
2. Description of the Related Art
The reflow soldering method is a method including preliminarily supplying a solder to a soldering position and melting the solder by using a heat source such as hot air blast, infrared radiation, and laser to thereby perform soldering. This method forms an increasing proportion of soldering methods in the recent electronic industry. This is mainly due to the fact that chip components have been used in place of conventional components with leads in concert with a reduction in size of electronic equipment and that a planar packaging method has been introduced to increase a packaging density, causing the necessity of precise and efficient soldering at a microscopic soldering region.
The electronic equipment is configured by soldering various electronic components to a substrate. Particularly, some field mainly including a computer field requiring high performance adopts a stepped soldering technique such that the melting points of solders bonding the electronic components mounted on the substrate are stepwise changed. The stepped soldering technique is mainly intended to prevent remelting of the solders bonding the mounted components due to thermal stress in the subsequent steps and also to after-solder a component having a low heat resistance.
In a conventional reflow soldering apparatus, electronic components mounted on a substrate are soldered by using an infrared radiation reflow furnace or a hot air blast furnace, for example, to apply heat to the substrate under substantially the same condition. Accordingly, in the case of applying the stepped soldering method to the conventional reflow soldering apparatus, a first soldering step using a solder having a higher melting point is first carried out and a second soldering step using a solder having a lower melting point is next carried out.
Accordingly, to perform reflow soldering using solders having different melting points, the stepped soldering technique must be adopted, so that much time is required to cause a reduction in soldering efficiency. Further, the conventional reflow soldering apparatus has another problem that it is difficult to melt only the solder having a higher melting point without melting the solder having a lower melting point on the same substrate and to thereafter resolder the same component for repair.
It is therefore an object of the present invention to provide a reflow soldering apparatus and a reflow soldering method which can simultaneously solder a plurality of electronic components by using a plurality of solders having different melting points under the atmospheric pressure.
It is another object of the present invention to provide a reflow soldering apparatus which can realize easy repair of a component soldered to a substrate by means of a solder having a higher melting point without melting a solder having a lower melting point on the same substrate.
In accordance with an aspect of the present invention, there is provided a reflow soldering apparatus for soldering a first component mounted on a substrate with a first solder having a first melting point and soldering a second component mounted on the substrate with a second solder having a second melting point higher than the first melting point, comprising heating means for substantially uniformly heating the substrate; a capsule for enclosing the second component; and evacuating means for decreasing the pressure in the capsule; the first component and the second component being reflow-soldered at substantially the same temperature by operating the evacuating means to decrease the pressure in the capsule by a given amount.
Preferably, the reflow soldering apparatus further comprises a pressure sensor for detecting the pressure in the capsule, a temperature sensor for detecting the temperature in the capsule, and a control unit for controlling the evacuating means and the heating means according to the pressure and the temperature respectively detected by the pressure sensor and the temperature sensor.
In accordance with another aspect of the present invention, there is provided a reflow soldering apparatus for selectively melting any one of solders bonding a plurality of components to a substrate, comprising heating means for heating the substrate; a capsule for selectively enclosing any one of the components bonded by the solder to be melted; and evacuating means for decreasing the pressure in the capsule; only the solder bonding the component selectively enclosed in the capsule being melted by operating the evacuating means to decrease the pressure in the capsule by a given amount.
After the solder bonding the component selectively enclosed in the capsule is melted, a solder is applied again to the substrate to carry out resoldering of the same component by remelting this solder.
In accordance with a further aspect of the present invention, there is provided a reflow soldering method comprising the steps of: applying a first solder having a first melting point to a first footprint formed on a substrate; applying a second solder having a second melting point higher than the first melting point to a second footprint formed on the substrate; mounting a first component on the substrate so that a lead of the first component comes into contact with the first solder; mounting a second component on the substrate so that a lead of the second component comes into contact with the second solder; enclosing the second component in a capsule; decreasing the pressure in the capsule; and heating the substrate to a temperature higher than or equal to the first melting point to simultaneously solder the first and second components.
In accordance with a still further aspect of the present invention, there is provided a reflow soldering apparatus for soldering a first component mounted on a substrate with a first solder having a first melting point and soldering a second component mounted on the substrate with a second solder having a second melting point higher than the first melting point, comprising: heating means for substantially uniformly heating the substrate; a capsule for enclosing the first component; and pressurizing means for increasing the pressure in the capsule; the first component and the second component being reflow-soldered at substantially the same temperature by operating the pressurizing means to increase the pressure in the capsule by a given amount.
The above and other objects, features and advantages of the present invention and the manner of realizing them will become more apparent, and the invention itself will best be understood from a study of the following description and appended claims with reference to the attached drawings showing some preferred embodiments of the invention.